[keyboard] Support paired delimiters (both wrap and surrounding pair)

[pokey]

• Have new keymapping for paired delimiters
• However, this keymapping is not global, so we need to think about how to have keymappings that aren't global
• Add a "wrap" action that expects a pair
• Add a "select surrounding pair" action that expects a pair
• Maybe add a "select any pair" mapping that doesn't expect a pair? Can get this with two keypresses from the above, but maybe useful to allow it as one keypress?